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Stringhalt is a disorder in horses characterized by high stepping with hyperflexion of the hind limbs. This disorder has been reported from the US, Australia, Chile, and Brazil. In most instances, the disease manifests itself in horses exposed to summer dandelion (Hypochaeris radicata). Stringhalt has been induced by feeding summer dandelion to a horse, thus directly implicating the plant. The causative agent or agents in the plant have not been identified. Characterization of a small laboratory animal model which would exhibit neuromuscular clinical signs and/or lesions when fed dandelion would greatly facilitate further studies to identify the active principle in Hypochaeris radicata. In this study
immature Rhode Island Red hybrid chicks were used as the animal model. Because chickens are bipedal, it was hypothesized that any signs of muscular degeneration affecting locomotion would be obvious. The chicks were divided into three treatment groups; the control, a 10 weight percent summer dandelion diet, and a 30 weight percent summer dandelion diet. Feed intake was measured daily and weights were recorded weekly. The chicks were fed this diet for 35 days, then humanly euthanized and necropsied. Heart, liver, spleen, leg muscles, the femoral and sciatic nerve, spinal cord and brain were taken for histopathology. There were no statistical differences in body weight, feed consumption, liver, or heart muscle weights between the different treatment group.
Silybum marianum, commonly known as milk thistle (MT), is reputed to be beneficial to liver health. The active ingredient in MT is silymarin, the biologically active ingredient from the MT seed. Dietary supplements of MT usually 70- 80% silymarin, can be purchased at common herbal supplement and health food stores, with recommendations that taking one to three capsules a day (200 mg of material per capsule, 80 % silymarin) may speed the regeneration of injured liver cells, and support, protect, and improve function of liver cells. The objective of this study was to determine if MT would reduce the toxic effects of pyrrolizidine alkaloids (PA) from tansy ragwort (TR) (Senecio jacobaea), including damage to
the liver, kidneys, heart, smooth muscles, and lungs. Chicks were randomly assigned to one of four treatment groups, with or without MT paired with two different concentrations of TR (0 and 5 weight percent). TR was mixed into the feed at the designed concentration and MT was administered twice daily via gavage. Feed intake, body weights and clinical signs were recorded throughout the study. Many of the chicks that had consumed the TR began to show signs of lethargy, loss of appetite, and weight differences before the end of the feeding trial. Two of the six chicks that had consumed the TR diet without MT, died before the end of the feeding period, on days 42 and 45. All chicks were humanely
euthanized 47 days after the start of experimental feeding and necropsied. At necropsy multiple chicks showed extensive liver damage, ascites, edema, enlarged spleen and low hematocrit. There was no difference in clinical effects or gross pathology between chicks receiving MT and TR when compared to those receiving only TR in their diet. Histological examination of the livers showed no differences between groups receiving MT and TR and those receiving only TR in their diet. Based on the results of this study, MT does not provide any level of protection TR induced liver disease.